#include "CityHash.h"

#ifdef WORDS_BIGENDIAN
#define uint32_in_expected_order(x) (bswap_32(x))
#define uint64_in_expected_order(x) (bswap_64(x))
#else
#define uint32_in_expected_order(x) (x)
#define uint64_in_expected_order(x) (x)
#endif

namespace Alice{
    static uint64 UNALIGNED_LOAD64(const char *p) {
        uint64 result;
        memcpy(&result, p, sizeof(result));
        return result;
    }

    static uint32 UNALIGNED_LOAD32(const char *p) {
        uint32 result;
        memcpy(&result, p, sizeof(result));
        return result;
    }
    static uint64 Fetch64(const char *p) {
        return uint64_in_expected_order(UNALIGNED_LOAD64(p));
    }

    static uint32 Fetch32(const char *p) {
        return uint32_in_expected_order(UNALIGNED_LOAD32(p));
    }

    namespace CityHash_Internal 
    {
        // Some primes between 2^63 and 2^64 for various uses.
        static const uint64 k0 = 0xc3a5c85c97cb3127ULL;
        static const uint64 k1 = 0xb492b66fbe98f273ULL;
        static const uint64 k2 = 0x9ae16a3b2f90404fULL;

        // Magic numbers for 32-bit hashing.  Copied from Murmur3.
        static const uint32 c1 = 0xcc9e2d51;
        static const uint32 c2 = 0x1b873593;
    }

    // A 32-bit to 32-bit integer hash copied from Murmur3.
    static uint32 fmix(uint32 h)
    {
        h ^= h >> 16;
        h *= 0x85ebca6b;
        h ^= h >> 13;
        h *= 0xc2b2ae35;
        h ^= h >> 16;
        return h;
    }

    static uint32 Rotate32(uint32 val, int shift) {
        // Avoid shifting by 32: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
    }

    template<typename T>
    void SwapValues(T& a, T& b)
    {
        T c = a;
        a = b;
        b = c;
    }

    #undef PERMUTE3
    #define PERMUTE3(a, b, c) do { SwapValues(a, b); SwapValues(a, c); } while (0)

    static uint32 Mur(uint32 a, uint32 h) {
        using namespace CityHash_Internal;

        // Helper from Murmur3 for combining two 32-bit values.
        a *= c1;
        a = Rotate32(a, 17);
        a *= c2;
        h ^= a;
        h = Rotate32(h, 19);
        return h * 5 + 0xe6546b64;
    }

    static uint32 Hash32Len13to24(const char *s, uint32 len) {
        uint32 a = Fetch32(s - 4 + (len >> 1));
        uint32 b = Fetch32(s + 4);
        uint32 c = Fetch32(s + len - 8);
        uint32 d = Fetch32(s + (len >> 1));
        uint32 e = Fetch32(s);
        uint32 f = Fetch32(s + len - 4);
        uint32 h = len;

        return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h)))))));
    }

    static uint32 Hash32Len0to4(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        uint32 b = 0;
        uint32 c = 9;
        for (uint32 i = 0; i < len; i++) {
            signed char v = s[i];
            b = b * c1 + v;
            c ^= b;
        }
        return fmix(Mur(b, Mur(len, c)));
    }

    static uint32 Hash32Len5to12(const char *s, uint32 len) {
        uint32 a = len, b = len * 5, c = 9, d = b;
        a += Fetch32(s);
        b += Fetch32(s + len - 4);
        c += Fetch32(s + ((len >> 1) & 4));
        return fmix(Mur(c, Mur(b, Mur(a, d))));
    }

    uint32 CityHash32(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        if (len <= 24) {
            return len <= 12 ?
                (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len)) :
                Hash32Len13to24(s, len);
        }

        // len > 24
        uint32 h = len, g = c1 * len, f = g;
        uint32 a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2;
        uint32 a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2;
        uint32 a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2;
        uint32 a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2;
        uint32 a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2;
        h ^= a0;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        h ^= a2;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        g ^= a1;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        g ^= a3;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        f += a4;
        f = Rotate32(f, 19);
        f = f * 5 + 0xe6546b64;
        uint32 iters = (len - 1) / 20;
        do {
            uint32 _a0 = Rotate32(Fetch32(s) * c1, 17) * c2;
            uint32 _a1 = Fetch32(s + 4);
            uint32 _a2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2;
            uint32 _a3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2;
            uint32 _a4 = Fetch32(s + 16);
            h ^= _a0;
            h = Rotate32(h, 18);
            h = h * 5 + 0xe6546b64;
            f += _a1;
            f = Rotate32(f, 19);
            f = f * c1;
            g += _a2;
            g = Rotate32(g, 18);
            g = g * 5 + 0xe6546b64;
            h ^= _a3 + _a1;
            h = Rotate32(h, 19);
            h = h * 5 + 0xe6546b64;
            g ^= _a4;
            g = bswap_32(g) * 5;
            h += _a4 * 5;
            h = bswap_32(h);
            f += _a0;
            PERMUTE3(f, h, g);
            s += 20;
        } while (--iters != 0);
        g = Rotate32(g, 11) * c1;
        g = Rotate32(g, 17) * c1;
        f = Rotate32(f, 11) * c1;
        f = Rotate32(f, 17) * c1;
        h = Rotate32(h + g, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        h = Rotate32(h + f, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        return h;
    }

    // Bitwise right rotate.  Normally this will compile to a single
    // instruction, especially if the shift is a manifest constant.
    static uint64 Rotate(uint64 val, int shift) {
        // Avoid shifting by 64: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
    }

    static uint64 ShiftMix(uint64 val) {
        return val ^ (val >> 47);
    }

    static uint64 HashLen16(uint64 u, uint64 v) {
        return CityHash128to64({ u, v });
    }

    static uint64 HashLen16(uint64 u, uint64 v, uint64 mul) {
        // Murmur-inspired hashing.
        uint64 a = (u ^ v) * mul;
        a ^= (a >> 47);
        uint64 b = (v ^ a) * mul;
        b ^= (b >> 47);
        b *= mul;
        return b;
    }

    static uint64 HashLen0to16(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        if (len >= 8) {
            uint64 mul = k2 + len * 2;
            uint64 a = Fetch64(s) + k2;
            uint64 b = Fetch64(s + len - 8);
            uint64 c = Rotate(b, 37) * mul + a;
            uint64 d = (Rotate(a, 25) + b) * mul;
            return HashLen16(c, d, mul);
        }
        if (len >= 4) {
            uint64 mul = k2 + len * 2;
            uint64 a = Fetch32(s);
            return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
        }
        if (len > 0) {
            uint8 a = s[0];
            uint8 b = s[len >> 1];
            uint8 c = s[len - 1];
            uint32 y = static_cast<uint32>(a) + (static_cast<uint32>(b) << 8);
            uint32 z = len + (static_cast<uint32>(c) << 2);
            return ShiftMix(y * k2 ^ z * k0) * k2;
        }
        return k2;
    }

    // This probably works well for 16-byte strings as well, but it may be overkill
    // in that case.
    static uint64 HashLen17to32(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        uint64 mul = k2 + len * 2;
        uint64 a = Fetch64(s) * k1;
        uint64 b = Fetch64(s + 8);
        uint64 c = Fetch64(s + len - 8) * mul;
        uint64 d = Fetch64(s + len - 16) * k2;
        return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d,
            a + Rotate(b + k2, 18) + c, mul);
    }

    // Return a 16-byte hash for 48 bytes.  Quick and dirty.
    // Callers do best to use "random-looking" values for a and b.
    static Uint128_64 WeakHashLen32WithSeeds(
        uint64 w, uint64 x, uint64 y, uint64 z, uint64 a, uint64 b) {
        a += w;
        b = Rotate(b + a + z, 21);
        uint64 c = a;
        a += x;
        a += y;
        b += Rotate(a, 44);
        return { (a + z), (b + c) };
    }

    // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
    static Uint128_64 WeakHashLen32WithSeeds(
        const char* s, uint64 a, uint64 b) {
        return WeakHashLen32WithSeeds(Fetch64(s),
            Fetch64(s + 8),
            Fetch64(s + 16),
            Fetch64(s + 24),
            a,
            b);
    }

    // Return an 8-byte hash for 33 to 64 bytes.
    static uint64 HashLen33to64(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        uint64 mul = k2 + len * 2;
        uint64 a = Fetch64(s) * k2;
        uint64 b = Fetch64(s + 8);
        uint64 c = Fetch64(s + len - 24);
        uint64 d = Fetch64(s + len - 32);
        uint64 e = Fetch64(s + 16) * k2;
        uint64 f = Fetch64(s + 24) * 9;
        uint64 g = Fetch64(s + len - 8);
        uint64 h = Fetch64(s + len - 16) * mul;
        uint64 u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9;
        uint64 v = ((a + g) ^ d) + f + 1;
        uint64 w = bswap_64((u + v) * mul) + h;
        uint64 x = Rotate(e + f, 42) + c;
        uint64 y = (bswap_64((v + w) * mul) + g) * mul;
        uint64 z = e + f + c;
        a = bswap_64((x + z) * mul + y) + b;
        b = ShiftMix((z + a) * mul + d + h) * mul;
        return b + x;
    }

    uint64 CityHash64(const char *s, uint32 len) {
        using namespace CityHash_Internal;

        if (len <= 32) {
            if (len <= 16) {
                return HashLen0to16(s, len);
            }
            else {
                return HashLen17to32(s, len);
            }
        }
        else if (len <= 64) {
            return HashLen33to64(s, len);
        }

        // For strings over 64 bytes we hash the end first, and then as we
        // loop we keep 56 bytes of state: v, w, x, y, and z.
        uint64 x = Fetch64(s + len - 40);
        uint64 y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
        uint64 z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
        Uint128_64 v = WeakHashLen32WithSeeds(s + len - 64, len, z);
        Uint128_64 w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
        x = x * k1 + Fetch64(s);

        // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
        len = (len - 1) & ~static_cast<uint32>(63);
        do {
            x = Rotate(x + y + v.lo + Fetch64(s + 8), 37) * k1;
            y = Rotate(y + v.hi + Fetch64(s + 48), 42) * k1;
            x ^= w.hi;
            y += v.lo + Fetch64(s + 40);
            z = Rotate(z + w.lo, 33) * k1;
            v = WeakHashLen32WithSeeds(s, v.hi * k1, x + w.lo);
            w = WeakHashLen32WithSeeds(s + 32, z + w.hi, y + Fetch64(s + 16));
            SwapValues(z, x);
            s += 64;
            len -= 64;
        } while (len != 0);
        return HashLen16(HashLen16(v.lo, w.lo) + ShiftMix(y) * k1 + z,
            HashLen16(v.hi, w.hi) + x);
    }

    uint64 CityHash64WithSeed(const char *s, uint32 len, uint64 seed) {
        using namespace CityHash_Internal;

        return CityHash64WithSeeds(s, len, k2, seed);
    }

    uint64 CityHash64WithSeeds(const char *s, uint32 len, uint64 seed0, uint64 seed1) {
        using namespace CityHash_Internal;

        return HashLen16(CityHash64(s, len) - seed0, seed1);
    }
}